[libre-riscv-dev] IEEE754 FPU turning into ALU with Reservation Stations

[Luke Kenneth Casson Leighton]

hi alexsander,

ok so taking copies of classes is generally frowned upon, as it results in
duplicated code, resulting in significant confusion and opportunities for
the duplicates to get out-of-sync.

if code is duplicated, it's expected to be different (different name,
different purpose).  there's no reason for FPState to be different, so
people will get terribly confused with an expectation that it *is*
different.

so i replaced the copy of FPState with an import of the one from
nmigen_add_experiment.py

converting the adder was... hair-raising, and has taken something like 3
weeks, ensuring at all times that the unit tests are functional at every
single step of the way, so as to make damn sure that all and any
incremental changes do not result in failure.

however, i can assure you that the alternative - starting from scratch with
a new class by commenting out the "old" one - will be hell.

let's work to get FPMul back up and running, first, ok?

l.